1. Field of the Invention
This invention relates generally to blow molding. In particular, this invention relates to mold assemblies for blow molding.
2. Description of Related Art
Blow molding is a cyclic process wherein a parison of material in a moldable condition is centered on the parting plane of a mold assembly, the mold assembly is closed around the parison, the parison is expanded so the exterior of the parison abuts molding surfaces defined by the closed mold assembly, the blow molded article is conditioned to be sufficiently rigid to retain its size and shape while unsupported, the mold assembly is opened and the blow molded article is removed. In general, the moldable condition of the parison is achieved when the material of the parison is at an elevated temperature, and the rigid condition of the blow molded article is achieved when the temperature of the material has been reduced. A blow molding machine comprises a press for opening and closing the mold assembly, blowing means for introducing a pressurized fluid (typically air) to expand the parison in the mold assembly, means for handling the molded article upon removal from the mold assembly and means for trimming waste from the molded article. Additionally, a blow molding machine may comprise heat transfer devices to elevate the temperature of the parison to achieve the moldable condition and to reduce the temperature of the blow molded article to achieve the rigid condition.
Blow molding is commonly used for production of containers wherein the blow molded article comprises a body portion defining a closed end and a neck portion connecting the body and a mouth opening, the mouth opening being an opening through which the blowing fluid is admitted to the container. Mold assemblies for blow molding containers comprise mating mold components wherein molding surfaces open to the mating faces of the mold components define the exterior of the container. Advantageously, the neck portion of the container comprises an exterior surface having a feature, such as a thread, called the “neck finish” for engaging a separable closure and the mating mold components comprise inserts for forming such features. In addition, the neck portion further comprises a dome element for handling the blow molded article, the dome element comprising waste of the blow molded article which is eliminated from the finished container. Advantageously, the dome element comprises an external groove to be engaged by handling means of a blow molding machine after removal of the molded article from the mold assembly. Inserts for forming the neck portion define the exterior surface of both the neck finish and the dome element. In known mold assemblies, the inserts are attached to the mating mold components by fasteners that are accessible only with removal of the mold assembly from the molding machine. Replacement of inserts of known mold assemblies to produce containers having a different neck finish or to refurbish inserts that are degraded through use requires time consuming disassembly of machine elements. Hence, a need exists to permit the replacement of inserts without such disassembly.